[radlad]

edit: The below text is not true, I didn't read the chart correctly - they are all different. (Inverse introversion/extraversion, but in the same order.)

ENFP and INFJ are actually very similar - if you believe in the personality test.

Despite the difference in letters, they share all the same cognitive functions, just in a different order.

https://www.typeinmind.com/nefi (ENFP)

https://www.typeinmind.com/nife (INFJ)

[dragonwriter]

If you have a system of four binary indicators, and swapping position on two of the four makes little difference, you probably have a very poor system.

[radlad]

Not to be snarky, but this is spoken like someone who hasn't tried to understand the system at all - not that I believe in it either.

Typically MBTI personality tests measure you based on four indicators: Extraversion/Introversion, Sensing/iNtuition, Thinking/Feeling, Judging/Perceiving

Each combination of indicators is given a "type." There are 16 possible types.

The MBTI personality test also defines 8 cognitive functions, believing that everyone must absorb information (perceiving) and turn it into actions/decisions (judging). It states that there are four ways of perceiving, and four ways of judging... extraverted/introverted sensing/intuition and extraverted/introverted thinking/feeling.

Each personality type has four cognitive functions associated with it: primary, auxiliary, tertiary, and inferior. You will have both an extraverted and introverted perceiving function as well as an extraverted and introverted judging function. Your primary cognitive function will match your introversion/extraversion trait, and then will flip back and forth between introversion/extraversion for the rest of your functions.

Since there are only 8 cognitive functions, and each personality type has 4, it's not surprising that they will often share cognitive functions - it also means that types can behave more similarly than one would expect based on their indicators.